On Jun 10, 3:01 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
Paul G. wrote:
On Jun 9, 9:35 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
Although Paul's suggestion to use the centering magnets would certainly
move the raster, the fact that it's fine with another analog board
indicates that it's actually the sweep timing that's off, not the
raster centering.
The control you're looking for is the "horizontal hold" or "horizontal
lock" or "horizontal frequency" control.
It's been so long, I can't remember what else I did to adjust the
display on these compact Macs. We're talking 12 to 15 years ago. I
seem to recall expanding the horizontal and vertical to fill the
screen- often that tiny screen had 1/4" or more of unused screen at
all four edges. Adjusting those magnets put the finishing touches on
the job.
The centering magnets will shift the raster, but not change its size.
Width and height should be adjusted by the correspondingly named
controls, if they are present, or can they be affected by the linearity
controls, though the linearity may suffer. ;-) On some monitors, even
the vertical hold control has an effect on raster height--such are the
imperfections of sweep circuits...
OK, I got off my butt and took another look at the analog bd in my
junk box. I then typed "mac plus" r55 r56 into Google and bingo, here
are the schematics and exactly the info needed to adjust and
troubleshoot:
http://home.earthlink.net/~gamba2/images/plus_analog.PDF
Looks like a leaky C1 would be the likely culprit for a horizontal
offset, detailed info on diagnosis and replacement is provided.